Continuous heat treatment furance



Oct. 24, 1939. TANNER 2,177,035

CONTINUOUS HEAT TREATMENT FURNACE Filed April 1, 1959 i z, j

;L .J L l 4 f c f d e 5 I ATTZEIiYS Patented Oct. 24, 1939 UNITED STATES PATENT OFFICE Application April 1, 1939, .Serial No. 265,504 In Great Britain April 1, 1938 2 Claims.

This invention is concerned with improvements in or relating to continuous heat treatment furnaces, and is particularly concerned with furnaces for the bright annealing of tubes and other ar- 5 ticles, which, prior to annealing, are produced by rolling, drawing, pressing, or other methods involving the use of oil or grease. If the articles coated with such oil or grease are subjected to an annealing treatment in .a furnace, the oil or grease volatilises at the volatilisation temperature of the hydrocarbon, and the vapours produced decompose at the cracking temperature which is below the annealing temperature, with the result that carbon is deposited on the articles.

With the object of overcoming this disadvantage, it has been proposed to subject the articles to a chemical degreasing treatment prior to the commencement of the heat treatment in the furnace. Such a process, however, is not only inconvenient, but also materially increases costs of production.

The principal object of the present invention is to provide an improved and simple construction of furnace which will avoid the deposition of carbon on the work, without resorting to chemical degreasing processes.

According to this invention, the furnace is provided with an inlet chamber maintained at a substantially constant temperature between the volatilisation temperature and the cracking temperature, so that the vapours produced by the volatilisation of the oil or grease can be removed before the work attains the temperature at which cracking takes place. Thus the vapours are removed before the introduction of the work into the treatment chamber, in which the higher annealing temperature would otherwise cause cracking of the vapours, and the deposition of carbon on the articles. The vapours may be removed 40 from the inlet or preheating chamber by a stream of reducing or non-oxidising gas flowing from the heat treatment chamber. A cooling chamber may be interposed between the inlet chamber and the treatment chamber to ensure that the stream of gases flowing from the latter enters the inlet chamber at a temperature below the cracking temperature of the vapours.

In order to enable the invention to be readily understood, reference will now be made to the accompanying drawing in which the figure is a side elevation illustrating diagrammatically one example of construction for carrying the invention into effect.

Referring to the drawing, the work, coated with oil or grease, is introduced into an inlet chamber a. and is annealed during its passage through a heat treatment chamber b, being finally discharged from the cooling or outlet chamber 0. The inlet chamber is preferably of greater length than is usual in continuous annealing furnaces 5 and comprises a temperature controlled zone (12 disposed between a cooling jacket e and an entry portion i for the work. The zone d is heated by appropriate auxiliary means, the temperature being controlled, for example, by pyrometers, and is 10 of such length that the work is maintained between the volatilisation temperature, and the cracking temperature of the oil or grease. The whole of the grease will thus be heated to above its volatilising temperature, while the vapours 15 thus produced will not be decomposed since the temperature remains below the cracking temperature. Thus the grease or oil is removed from the work before its introduction into the treatment chamber.

The flow of protective non-oxidising gas from the treatment chamber is utilized for entraining the vapours and discharging them through an outlet g on the entry portion 1. The discharge may take place into the atmosphere, or outlets g at the ends of the furnace may be connected in a circulating system including a pump h for returning the non-oxidising gas to the treatment chamber after the vapours have been removed in a condenser or oil filter i, a burner apparatus :i 0 being provided for removing oxygen from air admitted through the furnace ends. The provision of the cooling jacket e ensures that the non-oxidising gas entering the chamber d from the annealing chamber b is below the temperature of decomposition of the volatilised oil or grease.

Having described my invention what I claim and desire to secure by Letters Patent is:

1. The heat treatment in the heat treatment chamber of a continuous furnace of articles con- 0 taminated with oil or grease, comprising preheating the articles in an inlet chamber, maintaining the temperature in said inlet chamber at a substantially constant temperature between the volatilisation and cracking temperatures of the oil or grease, entraining the vapours produced by the volatilisation of the oil or grease in a. stream of a protective gas outfiowing from the treatment chamber, and cooling the protective gas between the treatment chamber and the inlet chamber to reduce its temperature below the cracking temperature of the said vapours.

2. The heat treatment in the heat treatment chamber of a continuous furnace of articles contaminated with oil or grease, comprising preheat- 55 ing the articles in an inlet chamber, maintaining the temperature in said inlet chamber at a substantially constant temperature between the volatilisation and. cracking temperatures of the oil or grease, entraining the vapours produced by the volatilisation of the oil or grease in a stream of a protective gas outflowing from the treatment chamber, and discharging the gases and vapours from the inlet chamber, removing the oil or grease, and returning the purified protective gas to the treatment chamber.

THQMAS GORDON TANNER. 

